well, with my 4blade 18x26 one rev should take me 26"

[tomcat rio]

at 3600rpm, the prop is turning at 1800 rpm(2:1 gearing)
so in a miniute i sould travel 3800 feet
3800 fpm"=.63 mi/min. or 37kts assuming no slip
at 3600 rpm i might get 22kts.
or 22/37
so it looks like i have a slip factor around 34% depending how you figger it..
...
seems high to me.
..i think something around a 20% is more normal.
..

[Mariner]

Where did you come up with the 20%? I think it varies VERY widely between boats.

[Elizabeth Ann]

Tomcat,

How did you make the jump from 1800 rpms at the prop to a distance of 3800 feet per minute. I guess you are using knowledge of the prop? One revolution at the prop is supposed to get you a distance equal to your prop pitch right?

[Elizabeth Ann]

Sorry, I didn't see the other thread.

[tomcat rio]

..read an areicle by a guy named Gere. he's aupposed to be a propulsion guru.